Window sash balance



F. J. DECKER ET AL sept. 16, 195s 2,851,721

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United States Patent O WINDOW SASH BALANCE Frederick J. Decker, Pittsford, and Mahlon H. Gregg,

Rochester, N. Y., assignors to The Caldwell Manufacturing Company, Rochester, N. Y., a corporation of New York Application June 25, 1954, Serial No. 439,396

Claims. (Cl. 16-197) This invention relates to an improved counterbalancing mechanism of a type suitable for use as a window sash balance.

It has been suggested that a weight such as a window sash be balanced by the tension and torsional forces of a single coil spring. The spring is attached to the window sash in such a manner that as the sash is lowered, the spring is elongated or tensed so as to exert a greater and greater upward force. A mechanism is provided for converting the torsional moment of the spring into an upward force. However, the mechanism is such that the upward force arising from the torsional moment of the spring decreases as the force caused by the tension of the spring increases. In this way the resultant upward force exerted by the tension and torsion of the coil spring can be constant throughout the travel of the sash so that the window sash may be moved with the same ease at any point in its travel.

ln order that the same sash balance may be used with lighter as well as heavier windows, means must be provided adjusting the resultant upward force exerted by the spring.

Accordingly, one of the features of this invention is the provision of a simple, reliable, easily operable means 'for adjusting the torsional moment of the spring.

It is a further object of the invention to provide a torsional adjustment for the spring that can be adjusted after the sash balance has been mounted in operating position.

In previous arrangements, the winding and unwinding of the spring as the sash is raised and lowered is produced by moving a spiral or helical actuating rod between followers at one end of a cylinder. One end of a coil spring is fastened to the cylinder so as to be rotated and the other end to be held stationary. However, unless the actuator is extremely large or rigid, it is apt to bend with use and become inoperable.

Therefore, in accordance with another feature of this invention, the actuator is stationary and the followers are moved along it as the window is raised or lowered.

It is apparent that the spring used in a sash balance of this` type must be of such structure that its tension is sufficiently great to support the weight of the window. This requires a large cross-section spring and any twisting thereof would require an extremely large force. Therefore, for some applications it may be found that it is too ditcult for the spiral actuator to twist the spring through the medium of the followers.

Accordingly, it is another feature of this invention to provide a reduction gear mechanism between the followers and the end of the spring that is twisted, thus making it easier for the motion of the followers along the spiral actuator to twist the spring, and reduce the number of turns of the windup of the spring.

Another object of the present invention is to provide means for reducing the frictional drag exerted on the rotating spring by the weight of the window.

The manner in which the features of the invention may be attained will be better understood after the following detailed discussion of the drawings, in which:

Fig. l is a partly sectional view of a sash balance embodying some of the features of this invention;

Fig. lA is an enlargement of the lower portion of Fig. l, and shows a modification thereof;

Fig. 2 is a partly sectional view of a sash balance using a reduction gear;

Fig. 3 is a cross-section ofV the reduction gear mechanism of Fig. 2;

Fig. 4 is a cross-sectional View showing a modication of a structural element of the sash balance shown in Fig. l, and

Fig. 5 is a perspective view of the modification shown in Fig. 4.

A window sash, a portion of which is indicated at 11 is attached to a lower end 13 of a sash balance designated generally 15. An upper end 17 of the sash balance 15 is attached to the window frame, a portion of which is indicated at 14. In accordance with the principles of the present invention, a spiral actuator rod 21 is attached to the window frame 14, by means to be hereinafter described in detail, and extends downwardly therefrom. A helical spring 23 is mounted on, and coaxial with, an upper spring carrier 25 and a lower spring carrier 27. A tube 29 encloses the spring 23 and the spring carriers 25 and 27.

ln accordance with the principles of the present invention the initial rotational position lof the spring 23 is adjustable, even after the sash balance 15 is in place in a window frame.

An upper end 31 of the upper spring carrier 25 is flanged and attached to the window frame as by screws 33. A slot 35 receives an end 37 of the spiral actuating rod 21. A washer 39 is positioned on the actuating rod 21 and the end 37 of the actuating rod 21 is split, thereby retaining the rod 21 stationary.

An adjusting cap 41 is positioned over the upper spring carrier 25 and is rotatable with respect thereto. The adjusting cap 41 has an aperture 43 therein which receives the spring 23 and the tube 29. A lug 45 of the mounting cap 41 extends into a slot 47 in the tube 29, and hence the tube 29 rotates when the mounting cap 41 is turned. The tube 29 has an indent 49 which forces two turns of the spring 23 into a slot 51 in a spring holder 53. The spring holder 53 is prevented from downward motion by a washer 55 which is fastened to the actuating rod 21. The washer 55 also prevents upward motion of the actuating rod 21 when the window is raised because the washer 55 is returned in position by spring holder 53 and the upper spring carrier 25.

The mounting cap 41 has cylindrical apertures 57 therein which are adapted to receive a nail or similarly shaped member. When the cap 41 is rotated by inserting a member into the slot 57, the tube 29 also rotates because of lug 45 which contacts a wall of the slot 47. This causes the upper end of the spring 2,3 to rotate around the upper spring carrier 25. The lower end of the spring 23 is now rotatably attached to the lower spring carrier 27 which is maintained non-rotatable unless the window is being raised by an actuating restriction 6l) that contacts stationary rod 21. Hence, the torsional force exerted by the spring 23 is adjusted and may be either increased or decreased by turning mounting cap 41 in one direction or the other.

In accordance with the principles of the present invention, both the longitudinal and the rotative displace ments of the spring 23 are altered by a movement of the window sash 11. Thus, both the torsion and tension forces exerted by the spring A21 are utilized to counterbalance the Weight of the window sash 11. It is necessary to utilize both forces because the force exerted on the window by tension alone is not constant over the eutire travel of the window, as mentioned above.

As aforementioned, the lower end of spring 23 is fastened to the lower spring carrier 27. The lower end 61 of the lower spring carrier 27 is outwardly flanged and is in contact with a nylon ball bearing 63 which is r0- tatably mounted on the lower spring carrier 27. A washer 65 is in contact with the upper surface of the nylon ball bearing 63 and supports a window strap 67 which is attached to the window sash 11, as by screws 69.

Assuming a downward movement of the sash 11, the lower spring carrier 27 moves downward, thereby increasing the length of the spring and hence the tensional force exerted on the sash 11. However, the downward motion of the lower spring carrier 27 causes the rotation thereof, because the actuating restriction 60 is in contact with the stationary spiral actuating rod 21. Hence, since the lower end of spring 23 is fixed to the lower spring carrier 27, the lower end of the spring is caused to rotate and unwind, thus decreasing the torsional forcing eX- erted by the spring 23.

To maintain the total force exerted on the sash 11 exactly constant the pitch of the helix on the spiral actuating rod 21 is varied as shown. The top of the rod is closely spiral and the bottom of the rod is loosely spiraled. Hence, at the bottom of the window travel, when the tensional force is great, only a small torsional force is exerted. While at the top of window travel, where the tensional force exerted is small, the torsional force is great, thereby enabling an even total force resultant to be applied to the sash 11.

A modification of the mounting cup 41 is shown in Figs. 4 and 5. In this modification slots 71 are formed in the head of the cap to enable a screw driver or a coin to be inserted therein to rotate the cap 41.

Another embodiment of the present invention is illustrated in Figs. 2 and 3. In this modification a reducing gear designated generally 81 is utilized at the bottom end of the lower spring carrier 27. The gear 81 is used when extremely heavy windows are to be balanced and is necessary because a heavy Window requires a heavy spring having a large cross-sectional area. With such a large cross-section too great an effort would be required to turn the spring.

The spring 23 is fixedly mounted to a spring carrier 83. A driving tube 85 is turned by the actuator rod 21. The tube 85 is attached to an eccentric gear 87 which turns a driven gear 89. The spring carrier 83 is attached to the driven gear 89. Hence, when the window is moved down, driving tube 85 turns, causing eccentric gear to walk around driven gear 87, rotating it. Since the spring carrier 83 is attached to the driven gear 87 the spring 23 is caused to rotate also, thereby exerting a torsional force. The number of teeth on gear 87 relative to gear 89 can be selected to give any desired force reduction.

While specific embodiments have been shown and dei scribed, it will of course be understood that various modifications may yet be devised by those skilled in the art which will embody the principles of the invention and found in the true spirit and scope thereof.

What is claimed as new and is desired to be secured by Letters Patent of the United States is:

l. A sash balance comprising in combination, a stationary spiral actuator, a coil spring mounted so as t0 encompass said actuator, means for keeping the upper end of said spring stationary, actuator contacting means for rotating the lower end of said spring as said contacting means moves relative to said actuator, said actuator means being positioned at a point remote from the point where said coil spring is secured to a torque tube, and means for mounting the lower end of said actuator contacting means for longitudinal movement with a window 21 sash but enabling relative rotational motion with respect thereto.

2. In a sash balance as set forth in claim l, means accessible when said sash balance is mounted in said window frame for rotating the upper end of said spring with respect to the lower end whereby the initial torsion is infinitely adjustable, without detaching the sash balance from the window frame.

3. A sash balance as set forth in claim 1 wherein the means for holding the upper end of said spring stationary is a cylinder having a larger diameter than the inner diameter of the spring, and upon which the spring is fused, and wherein means are provided for unwinding said spring so as to loosen its grip on said cylinder.

4. A sash balance as set forth in claim l wherein a reduction gear is coupled between said actuator contacting means and the lower end of said spring, thereby enabling it to be utilized in said sash balance, exerting a constant upward force.

5. A sash balance as set forth in claim l wherein means for mounting the lower end of said actuator contacting means for rotation with respect to a window iucludes a friction reducing means.

6. A sash balance comprising in combination a spiral actuator, means for fastening one end of said actuator to the side of a window, a sash balance coil spring mounted about said actuator, means for fastening one end of said spring so that it is fixed relative to the side of said window, means for connecting the other end of said spring to the sash to be balanced, said connecting means being such as to permit said other end of said spring to rotate with respect to said sash but preventing longitudinal movement with respect thereto, and means including followers for twisting said other end of said spring as said sash moves along said actuator, said followers having an inclined plane and being positioned at a point remote from where said spring is attached to a torque tube.

7. A sash balance comprising in combination a cap adapted for attachment to the side of a window, a spiral actuating rod rigidly mounted in said cap, a longitudinally coiled sash balance spring, means for mounting said coil spring so that one end is fixed relative to said cap and so that the axis of said spring coincides with the axis of said actuating rod, an annular member having a larger inside diameter than the largest cross-sectional dimension of said actuating rod, means for fastening said annular member to the other end of said spring in such manner that the axis of said annular member coincides with the axis of said rod, followers mounted on said annular member, said followers being adapted to follow the spiral of said actuator and turn said other end of said spring as it moves along said actuating rod, and means mounting said annular member to a sash that is to be balanced in such manner that said annular member may rotate with respect to said Sash and that said annular member may be carried by said sash in a direction which elongates said spring.

8. A sash balance as defined in claim 7 wherein said annular member is in the form of a cylinder which surrounds said actuator and lies within said spring, which extends from said other end of said spring to which it is fastened to a point well within said spring and wherein said followers are mounted at the end of said cylinder that is within said spring.

9. A sash balance comprising a spiral actuator rod having the upper end thereof fixedly attached to a window frame and having the lower end thereof free, a coiled balance spring, a spring-supporting tube for mounting said coiled balance spring on said spiral actuator rod, actuating contacting means connecting said tube to said spring in such a manner as to enable rotation and translation therebetween, a window supporting nylon bearing rotatably mounted on the lower end of said tube,

and means for supporting a window on said rotatable nylon bearing, thereby lessening friction therebetween.

10. A sash balance attached to a window frame for balancing the weight of a slidable window comprising an upper spring carrier anchored to said window frame, a spiral actuating rod lixedly attached to said upper spring and depending therefrom, said spiral actuator rod being coaxial with said upper spring carrier, a helical spring mounted on said upper spring carrier and coaxial therewith, a mounting tube coaxial with, and enclosing, said spring, a mounting cap positioned'on said upper' spring carrier and having an aperture therein, said aperture being adapted to receive an end of said mounting tube and an end of said spring, means attaching said end of said mounting tube to said mounting cap to prevent relative rotation therebetween, means for attaching said spring to said mounting tube to prevent relative rotation therebetween, said mounting tube, said mounting cap, and said spring being rotatable with respect to said spiral actuator rod, a lower spring carrier, means attaching the other end of said spring to said actuator rod, restriction -means References Cited in the file of this patent UNITED STATES PATENTS 2,041,646 Larson May 19, 1936 2,477,069 Larson July 26, 1949 2,577,953 De Vries et al Dec. 11, 1951 2,604,655 Peremi July 29, 1952` 2,622,267 Peremi Dec. 23, 1952 FOREIGN PATENTS 1,047,390 France July 22, 1953 

